Tektronix Grass Valley 3000 - Manual (Page 120)

3-12
Section 3 — Switcher Concepts
Linear Key
A linear key is similar to a luminance key except that the gain of
the key is set to a value of one (also called “unity”) so that the
edges of anti-aliased key sources are faithfully reproduced. Anti-
aliased sources, such as the output of a character generator or
graphics system, have soft edges that produce a mix between the
fill and the background at the key edge. A linear key preserves
this edge, as well as DPM soft edges, drop shadows, etc.
Preset Pattern Key
A preset pattern key or preset wipe is a key in which the shape of a
wipe pattern cuts the hole in the background video. The fill video
is selected on the Key bus, and the Wipe pattern controls and
menus are used to select and adjust the key source pattern.